Ring member and method of making same



Oct. 23, 1928'.

B. STEENSTRUP RING MEMBER AND METHOD .OF MAKING SAME Filed May 29, 1926 Hi s Attorn ey.

InventOr Christian Steenstrgp,

Patented Get. 23, 1928.

UNlTED STATES 1,688,762 PATENT oFFica.

CHRISTIAN STEENSTRUP, OF SCHENECTADY, NEW YORK, ASSIGNOR T GENERAL ELECTRIC COMPANY, A COB-PQRATION OF NEW YORK.

RING MEMBER AND METHOD OF MAKING SAME.

Application filed May" 29,

My invention relates to ring members which are formed by tightly winding up strips of sheet metal. Such ring members have been used in the construction of various nied by considerable difiiculty in causing the turns to lie sufliciently close against each other at all points so as to produce a firm and solid structure. Where the strip is comparatively narrow this result may be accom- 'plished by winding up the strip in a heated condition, spot-welding it at intervals and afterward copper-brazing it as described 111 my Patent No. 1,528,581, March '8, 1925, but this method is not applicable where the str p is relatively wide and it is under such conditions that the greatest di'fiiculty hasbeen experienced due no doubt in a large measure to irregularities in the material being wound.

It is an object of my invention to provide 5 an improved wound-up ring structure which shall have the desired firmness and solidity irrespective of the width of the strip from which it is wound, together with a method of making the same. b My invention will be better understood from the following description taken in con nection with the accompanying drawing, and its scope will be pointed out in the appended claims.

Referring to the drawing, Fig. 1 shows a sheet steel strip being creased and wound up into a ringon a mandrel; Fig. 2 shows the ring removed from the mandrel; Fig. 3 shows the ring in a press about to be expanded; Fig. 4 shows the expanded ring comprising a dynamo-electric machine frame provided with supporting feet; and Fig. 5 shows the ring forming the central frame member of an enclosed'dynamo-electric machine.

In the drawing, I have shown in Fig. 1, the strip 1, which may be of steel or other suitable material, being wound up on the mandrel 2 to form the ring 3, suitable tension being of course applied to the strip to cause it to wind up in a proper manner. After the winding operation is completed the ends of the strip are firmly secured to the adjacent turns, for example, by welding as at 4 and 5, to prevent unwinding. The ring- 3 is then subjected to an expanding operation where- 1926. Serial No. 112,715.

by the material of the ring is stretched be yond its elastic limit. As an example of one way by which this expansion may be produced, I have shown in Fig. 3 a portion of a press 6 having a ring 7 of a suitable size for supporting the ring 3. Through the ring 3 is forced the drift 8 having a slight taper 9 at its entering end. The diameter of the body of the drift is such that when it is forced into the ring 3 it stretches the material forming each of the several turns or layers to a point beyond the elastic limit of the material thereof, causing itto take a permanent set. It will of course be understood that in this expanding process the welding of the ends of the strip prevent unwinding or slipping of the turns. In the drawing 1 have not attempted to show the material forming the strip having a thickness of the proportion which would probably be used commercially, the thickness being purposely exaggerated for convenience'in illustrating the invention. The weld 4 on the interior of the ring may form a ridge which may be machined ofl prior to the expanding opera-v tion, however, it may be found more expedientto form a channel on the side of the drift 8 to receive the ridge formed by the weld. The drift in being forced through the ring applies the expanding force'directly to the innermost layer or turn which in stretching;

the material of the several layers or turns contracts in accordance with the natural elasticity of the material with the important result that the several layers are left thereafter under a certain amount of permanent stress, causing them to hu each other tight- 1y. The reason for this is plain when one considers that the material of all of the layers will contract circumferentially an equal amount when the drift is removed, all having been stretched beyond the elastic limit. The total circumferential contraction of the outermost layer will by reason of its longer length be greater than the total circumferential contraction of the innermost layer and since the diameters of circles are proportional to their circumferences it follows that in the natural contraction of the material of the layers or turns of the ring the reduction in diameter of the outermost layer would be greater than the reduction-in diameter of I of the layers 0 the ring to the copper brazing process described in my aforesaid patent, but under ordinary circumstances such will probably not.

be found necessary.

order; to revent any possible slipping f the ring axially with respect to each other the strip from which the ring is wound may first be slightly creased so that in the finished ring the layers shall interlock as well as tightly hug each other. In Fig. 1, Ihave shown by way of example one way in which such a crease may be formed. Here two pairs of complementary rollers 10 are shown through which the strip in passing to the mandrel is given the two creases 11. The depth of these creases need be only slight and for the purposes of illustration are necessarily shown exaggerated. Creasing of the strip to prevent axialdisplacement of the layers may befound particularly desirable in the ease of relatively short rings and where the end faces of the ring are to be machined or otherwise subjected to end thrusts, however, where the rings are relatively long the frictional engagement of the respective layers with each other may be sufiieient to make creasing unnecessary.

In Fig. 4 of the drawing I have shown the ring 3 after being subjected to the expanding process as forming the frame of a dynamo-electric machine and provided with supports 12 which-may be suitably secured to the ring as by welding or brazing. In Fig.

5 the ring 3 also forms the frame or body of a dynamo-electric machine, but in this case it is supported by means of the end heads 13 having feet 14 and providing bearings 15 for the shaft 16.

While I-have described my invention as applicable to a dynamo-electric machine, it is to be understood that it is by no means limited to such but on the contrary may have many other uses, nor is it at all limited to wound-up structures inwhich the material is relatively wide inasmuch as the method is equally applicable to the use of both narrow and wide strips.

What I claim as new and desire to secure by Letters Patent of the United States, is 2- l. The method of forming a built-up ring member from a sheet metal strip which comprises winding upthe strip into a ring having a plurality of turns, securing together portions thereof to prevent unwinding of'the ring thus formed and expanding the ring beyond the elastic limit of" the material thereof dynamo-electric machine from a strip of magnetic material which comprises longitudinally creasing the strip, winding up the strip into a ring haying a plurality of turns, welding the ends of the strip to the adjacent turns to prevent unwinding, applying an expanding force to the interior of the ring such that the material in substantially all of the turns is stretched beyond its elastic limit, and removing the expanding force.

4E. A frame structure for a dynamo-electric machine comprising a plurality of radial- -1y superposed layers forming a ring, the successive layers being under stress, the magnitude of the stress varying in a regular manner from the innermost layer to the outermost layer whereby each layer hugs the layer next within.

5. A frame structure for a dynamo electric machine comprising a wound-up sheet metal ring, the successive superposed layers of which have interlocking creases to prevent relative axial displacement thereof, the material of the successive layers being under a stress which causes them to tightly hug each other.

In witness whereof, I have hereunto set my hand this 28th day of May, 1926' CHRISTIAN STEENSTRUP. 

